The Philadelphia Eagles aren't the only football franchise turning in a disappointing performance this season. Some Web sites offering fantasy football have suffered from outages and other glitches that have left many players infuriated.

Consider Fahim Ahmad in Durham, N.C., who tried a new free service from Walt Disney Co.'s ESPN.com this year. In fantasy football, fans draft their own teams of pro players, earning points based on the players' real-life performances. The Web sites track users' scores and provide related news and statistics. But Mr. Ahmad, 27, and his friends couldn't access ESPN's site to view lineups and scores during the first few weeks of the football season, which started in September.

"I guess ESPN just didn't expect fantasy to be so big this year," says Mr. Ahmad. He was so frustrated that he later transferred his league to a rival service. ESPN.com says it has since corrected the site's errors.

Technology and media companies such as Yahoo Inc., Electronic Arts Inc. and ESPN have piled into fantasy football, attracted by fanatical users who can drop hundreds of dollars a year to see who is the best armchair general manager. For the companies, it doesn't hurt that the players are typically young, college-educated males with plenty of disposable income, a dream demographic for many advertisers.

But consumers' reactions to the recent site hiccups illustrate how expectations for Internet services are rising. The expansion of fantasy sports has brought mainstream users who want the same availability of the sites as they would of their telephone or television -- expectations some fantasy sports sites concede they aren't always able to meet.

Fantasy leagues have been around for decades, but exploded in popularity once the Internet made it easy to keep statistics centrally and update scores automatically. Football boasts the biggest fantasy following, with more than 12 million players, according to the Fantasy Sports Trade Association. Some fantasy football services charge players, with consumers spending roughly $150 on average on entry fees and related services annually.

This season, companies including ESPN.com and News Corp.'s Fox Sports Interactive launched free fantasy football offerings to garner new users. But the companies -- like their rivals, paid and unpaid -- say the services are challenging to operate. The sites must display statistics for thousands of fantasy teams, all of which have different player combinations. Rules vary, but a fantasy-football player might earn six points if a quarterback on his roster throws a touchdown pass, for example, or if a receiver on his team catches one.

Several services rely on third-party providers for up-to-the-minute statistics; those feeds sometimes falter. Officials at several fantasy services say demand this year also outstripped projections. "There is no Sunday that goes by without some problem. Your customer service has to be really good," says Steve Snyder, general manager of Viacom Inc.'s CBS SportsLine.com, which charges $150 per league for its flagship fantasy service and doesn't offer a free option.

ESPN.com, which has long offered paid services, rolled out its first free service before the start of the season. It says it quickly attracted five times as many players as it had in the past, though it declined to provide numbers. ESPN's paid services allow users to view live scoring updates, read weekly analysis of individual players and win special prizes.

But both paying and non-paying users cursed their computer screens as they struggled to access the site or view scores on the first two Sundays of the season. Some players couldn't complete roster changes before game days. In mid-September, John Kosner, senior vice president at ESPN.com, emailed an apology to players saying the company "shares your frustration."

Mr. Kosner says ESPN.com ran into network troubles at a data center in Seattle on the first Sunday of the season. A week later, it encountered problems trying to access the National Football League's official data "feed" of game statistics. The site has since avoided any major mishaps, Mr. Kosner says.

Fox Sports Interactive's fantasy football service, developed and operated in partnership with Microsoft Corp.'s MSN unit, also ran into technical problems. From the season's start through recently, users reported gripes such as scoring errors and problems making changes to their lineups.

Daniel Ramirez of Pasadena, Calif., says he couldn't access his team's roster or check scores four or five times during the season using the Fox service. "I waited it out, and usually it was fixed" by the next day, he says. The 35-year-old adds he won't return to Fox next year.

Fox says it sorted out most snafus in the first few weeks of the season. "That kind of stuff is going to happen," says Brian Grey, general manager of Fox Sports Interactive. "Our focus is on getting back in the market with an even better product in 2006."

Yahoo, which has offered its own fantasy football service since 1999, also fumbled the ball. The Sunnyvale, Calif., company's services were unavailable for a portion of Nov. 30. Will Leitch, editor of sports Web log Deadspin, says he received about 70 emails in 90 minutes from Yahoo users after he wrote about the malfunction that day. "People were freaking out," says Mr. Leitch.

David Katz, Yahoo's head of sports and entertainment, says the service was out for a few hours. Inconvenience for fantasy football players was minimal, he says, since the outage happened mid-week when no actual games are played.

But some fantasy-team owners say that with pride and money at stake, they can't tolerate even intermittent problems. If a fantasy team owner can't access a site on a Tuesday morning, for example, he may be unable to acquire a key free agent player who has been let go by another team in the league.

Ori Schwartz of Tenafly, N.J., launched a free, ad-supported fantasy football service called FleaFlicker.com this year after leaving his full-time software job. Mr. Schwartz, 24, says he attracted several hundred users who abandoned other services. Those who switched to FleaFlicker didn't hide their bitterness, naming their leagues with monikers such as "ESPN dropped ball" and "Foxsports Sucks."